(1) Field of the Invention
The present invention relates to a method for producing ultralow-resistance current sensors and an apparatus for processing the same.
(2) Description of the Prior Art
The ultralow-resistance current sensor, also called the current-sensing resistor, a kind of current-induced electronic elements whose resistances are ranged between 0.1Ω and 0.0005Ω, is usually used for monitoring working voltages of various circuit designs. For example, the ultralow-resistance current sensor can be used as a recharge indicator for batteries, or a monitor for working currents or working voltages. In particular, the ultralow-resistance current sensor is now playing an important role in energy-saving and carbon-reduction design.
Current sensors can be manufactured by microlithography or by punching process, which has the advantage of maintaining metallic characteristics. However, microlithography can produce only current sensors of sizes larger than 1206. Cost is high, and deep grooves are difficult to achieve. The process is also time-consuming and liable to environmental protection issues. Further, the current sensors manufactured by punching are restricted to sizes larger than 4518. It is therefore not easy to miniaturize electronic elements by metal manufacturing processes to meet the requirement of portable electronic devices.
On the other hand, the size of the ultralow-resistance current sensor can be significantly reduced by the thin-film process, in which non-solid metallic material is applied on a substrate, ceramic or otherwise, to form the basic structure of the ultralow-resistance current sensor. In this light, the size of the ultralow-resistance current sensor can reach 0201. However, this process changes metallic configurations, deteriorates metallic characteristics, and results in significantly elevated resistance in response to in creasing ambient temperature. Thus, although the thin film process can miniaturize the ultralow-resistance current sensor, it yields products with high measurement errors, which is causes for major concerns; in particular, for the high-end products of portable electronic devices.